This invention relates to gas mixing and supply apparatus.
Pressurised gases, typically carbon dioxide, are commonly used for the dispensing of carbonated beverages such as beer and lager. With certain beverages, however, it is desirable or even essential to use a mixture of pressurised gases, for example carbon dioxide and nitrogen. In those cases, it is usually necessary not only for the mixture constantly to contain more or less predetermined proportions of the constituent gases (e.g. 70% volume nitrogen and 30% volume carbon dioxide) but also for the working pressure (i.e. the pressure applied to the beverage to dispense it) to be maintained within fairly specific limits. Hitherto, this has been achieved by providing a source of pressurised gas mixture specifically for use with the beverage in question. In particular, specially designed kegs each having a beverage-containing cavity and a separate pressurised gas-containing cavity have been used. Not only are those very expensive to produce, but also it would be advantageous to be able to utilise, as the source of the carbon dioxide constituent of the mixture, the source thereof used to dispense other carbonated beverages on the same premises, the other constituent(s) of the mixture, such as nitrogen, being mixed with it on the premises. It is an object of the present invention to provide means for achieving this, having regard to the mixture composition and pressure criteria referred to above.